Was evaluating adding spell check to a product I own. As per my research the major decisions that need to be made:
I've used Hunspell for a few things, and I don't really have any horror stories with it. I've only used it with English (American) though, but it claims to work with other languages.
As for licensing, it offers a choice of GPL, LGPL, and MPL. If you don't like the MPL, you can always choose to use the LGPL.